Provision of coverage for a wireless communication network by using moving base stations on robots or drones

ABSTRACT

A system, methods, apparatuses, and computer programs for providing coverage of a wireless communication network are described. The wireless communication network comprises radio base stations ( 150 ) mounted on mobile robots ( 100 ) and the mobile robots ( 100 ) are capable of communicating with a maintenance base ( 110 ). The method comprises to determine a radio coverage area ( 140 ) to be provided by the base stations mounted on said mobile robots ( 100 ). The method further comprises to deploy said mobile robots ( 100 ) at geographical positions suitable to provide the radio coverage area ( 140 ) and the maintenance base ( 110 ) replacing a deployed mobile robot ( 100 ) in order to maintain the radio coverage area ( 140 ).

TECHNICAL FIELD

The present invention relates to telecommunications, and in particularto methods, apparatuses, and computer programs for providing coverage ofa wireless communication network.

BACKGROUND

Unmanned aircraft vessel, unmanned land vehicle, and unmanned marinevessel are types of vehicles that move autonomously without human pilot,either autonomously on a pre-programmed path or steered from remote.These vehicles could operate respectively in the air, on the land, onsea, or on inland water. The vehicles typically have an own enginerespectively jet, propeller, wheel, crawler, propeller screw, or hoverpropulsion and gear. These are vehicles are known under the generic termmobile robots.

The increasing capabilities, high movability and the recently decreasingprice of mobile robots suggest utilizing mobile robots also in newdeployment areas, for example in wireless communication networks.

There are situations when the need for network capacity grows rapidlyand it is urgent to create more and/or remote network coverage in anad-hoc fashion. This could be caused by a movement of people likeevacuation, road jam, or huge public events. Today there is a need toinstall base stations or wireless access points at these places andconnect them with the wireless communication network. This is howeversometimes impossible due to character of the terrain or area property,or simply because the network coverage or network capacity demandschange too fast or unexpected.

A utilization of mobile robots in mobile communication networks promisesseveral benefits such as quick deployment, quick withdrawal, and highcoverage flexibility. In order to achieve these benefits appropriatemethods and devices are needed that enable provisioning of coverage of awireless communication network with the help of mobile robots and waysto maintain the achieved coverage also in cases that mobile robots failunexpectedly or have to be periodically recharged/refueled.

SUMMARY

There is a clear need for providing coverage of a wireless communicationnetwork with mobile robots. This is solved by mounting radio basestations on mobile robots. There is also need to also maintain theprovisioned coverage even when deployed mobile robots have to bereplaced. The need to replace a mobile robot may arise due to suddenfailure of a mobile robot or due to foreseeable maintenance needs suchas refueling or recharging.

It is an object of the present invention to provide coverage of awireless communication network with the help of radio base stationsmounted on mobile robots. This object is achieved by the independentclaims. Advantageous embodiments are described in the dependent claims.

According to an exemplary aspect of the invention, a method forproviding coverage of a wireless communication network is provided. Thewireless communication network comprises radio base stations mounted onmobile robots and the mobile robots are capable of communicating with amaintenance base. The method comprises to determine a radio coveragearea to be provided by the radio base stations mounted on said mobilerobots. The method further comprises to deploy said mobile robots atgeographical positions suitable to provide the radio coverage area; andto replace, by the maintenance base, a deployed mobile robot in order tomaintain the radio coverage area.

The method may further comprise that replacing a deployed mobile robotcomprises to instruct the deployed mobile robot to be replaced to returnto the maintenance base; and to deploy a further mobile robot to avacant geographical position.

The method may further comprise to re-arrange the deployment of themobile robots to geographical positions.

According to another exemplary aspect of the invention a method ofoperating a mobile robot is provided. The mobile robot comprises a radiobase station of a wireless communication network and the mobile robot iscapable of communicating with a maintenance base. The method comprisesto take up a geographical position on instruction. The method furthercomprises to provide a radio coverage area or sub-area at thegeographical position. The method further comprises to move, oninstruction, to a further geographical position while continuing toprovide the radio coverage area or sub-area and to return, oninstruction, to the maintenance base.

The method may further comprise to determine a condition that a returnto the maintenance base is required and to initiate handing overhandling of calls and/or packet sessions ongoing in the base station ofthe mobile robot to a further mobile robot.

The method may further comprise to determine a condition that a returnto the maintenance base is required, comprising of determining anoperational status, determining the operational status to be critical,sending a status report to the maintenance base comprising theoperational status; and receiving an instruction from the maintenancebase to return to the maintenance base.

According to another exemplary aspect of the invention a method ofoperating a maintenance base for providing coverage of a wirelesscommunication network is provided. The wireless communication networkcomprises radio base stations mounted on mobile robots and the mobilerobots are capable of communicating with the maintenance base. Themethod comprises to determine geographical positions for the mobilerobots. The method further comprises to deploy said mobile robots at thedetermined geographical positions by instructing them to take up theirdetermined geographical positions, and to replace a deployed mobilerobot.

The method may further comprise that replacing a deployed mobile robotcomprises to instruct the deployed mobile robot to be replaced to returnto the maintenance base and to deploy a further mobile robot to a vacantgeographical position.

The method may further comprise to re-arrange the deployment of themobile robots to geographical positions.

According to another exemplary aspect of the invention a mobile robot isprovided comprising a radio base station of a wireless communicationnetwork. The mobile robot is capable of communicating with a maintenancebase. The mobile robot is capable of on instruction taking up ageographical position. The mobile robot is further capable of providinga radio coverage area or sub-area at the geographical position. Themobile robot is further capable of, to move to a further geographicalposition on instruction while continuing to provide the radio coveragearea or sub-area and to return, on instruction, to the maintenance base.

According to another exemplary aspect of the invention a maintenancebase for providing coverage of a wireless communication network isprovided. The wireless communication network comprises radio basestations mounted on mobile robots and the mobile robots are capable ofcommunicating with the maintenance base. The maintenance base is capableof determining geographical positions for the mobile robots. Themaintenance base is further capable of deploying said mobile robots atthe determined geographical positions by instructing them to take uptheir determined geographical positions; and to replace a deployedmobile robot.

According to another exemplary aspect of the invention a system forproviding coverage of a wireless communication network is provided. Thewireless communication network comprises radio base stations mounted onmobile robots and the mobile robots are capable of communicating with amaintenance base. The system comprises a plurality of mobile robots, atleast one maintenance base, and at least one user equipment.

The foregoing and other objects, features and advantages of the presentinvention will become more apparent in the following detaileddescription of embodiments of the invention illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomebetter apparent from the detailed description of particular but notexclusive embodiments, illustrated by way of non-limiting examples inthe accompanying drawings, wherein:

FIG. 1 shows a diagram illustrating a system for providing coverage of awireless communication network according to the invention;

FIG. 2 shows an illustration of mobile robots taking up geographicalpositions from the maintenance base, according to the invention;

FIG. 3 shows an illustration of a daisy chain loop of deployed mobilerobots, and a circular shift operation, according to the invention.

FIG. 4 shows an illustration of a plurality of daisy chain loops, alltogether forming a mobile coverage area, according to the invention;

FIG. 5 shows an illustration of a double daisy chain loop, according tothe invention;

FIG. 6 shows an illustration of a replacement of a failing mobile robotfrom a deployment buffer, according to the invention;

FIG. 7 shows a first flow diagram in a mobile robot, according to theinvention;

FIG. 8 shows a second flow diagram in a mobile robot, according to theinvention;

FIG. 9 shows a first flow diagram in a maintenance base, according tothe invention;

FIG. 10 shows a second flow diagram in a maintenance base, according tothe invention;

FIG. 11 shows a block diagram illustrating a mobile robot, according tothe invention;

FIG. 12 shows a block diagram illustrating a maintenance base, accordingto the invention;

DETAILED DESCRIPTION

In the following, methods, apparatuses, and computer programs forproviding coverage of a wireless communication network according to theinvention are described in more detail.

Within the context of the present application, the term “mobile robot”refers to an automatic machine that is capable of moving in any givenenvironment. Mobile robots have the capability to move around in theirenvironment and are not fixed to one physical location. In contrast,industrial robots usually consist of a jointed arm (multi-linkedmanipulator) and gripper assembly (or end effector) that is attached toa fixed surface. Mobile robots may be classified by:

The environment in which they move:

-   -   Land or home robots are usually referred to as Unmanned Ground        Vehicles. They are most commonly wheeled or tracked, but also        include legged robots with two or more legs (humanoid or        resembling animals or insects).    -   Aerial robots are usually referred to as Unmanned Aerial        Vehicles.    -   Underwater robots are usually called Autonomous Underwater        Vehicles or Unmanned Submarine Vessel.    -   Water surface based mobile robots are usually referred to as        Unmanned Marine Vehicles.

The above listed vehicles are the types of vehicles that moveautonomously without human pilot on a programmed or instructed path ortowards an instructed geographical position, or may also be steered andcontrolled remotely. These vehicles could operate respectively in theair, on land, underground, on sea and inland waters, in space or even onother planets/asteroids. The vehicles have an own engine respectivelyjet, propeller, wheel, crawler track, propeller screw, or hoverpropulsion and gear. The vehicles have the ability of sending data toeach other and/or to a controlling base wirelessly.

Within the context of the present application, the term “daisy chain”refers to an association scheme, used for example in electrical andelectronic engineering in which multiple objects are associated togetherin a sequence or in a ring. The daisy chain within the context of thepresent application forms a ring topology, i.e. there is a loopconnection back from the last device to the first. For example thesequence of A-B-C-D-E and then back to -A (loop), wherein A-E are thesequenced objects. This is here referred to as a “daisy chain loop”.

Within the context of the present application, the term “geographicalposition” refers to a fixed geographical location or a trajectory pathbetween two geographical locations.

Within the context of the present application, the term “user equipment”(UE) refers to a device for instance used by a person for his or herpersonal communication. It can be a telephone type of device, forexample a telephone or a SIP phone, cellular telephone, a mobilestation, cordless phone, or a personal digital assistant type of devicelike laptop, notebook, notepad equipped with a wireless data connection.The UE may also be associated with non-humans like animals, plants, oreven machines. A UE may be equipped with a SIM (Subscriber IdentityModule) comprising unique identities such as IMSI (International MobileSubscriber Identity) and/or TMSI (Temporary Mobile Subscriber Identity)associated with a subscriber using the UE. The presence of a SIM withina UE customizes the UE uniquely with a subscription of the subscriber.

Within the context of the present application, the term “wirelesscommunication network” may particularly denote a collection of nodes orentities, related transport links, and associated management needed forrunning a service, for example a wireless telephony service or awireless packet transport service. Depending on the service, differentnode types or entities may be utilized to realize the service. A networkoperator owns the wireless communication network and offers theimplemented services to its subscribers. Typical examples of a wirelesscommunication network are radio access network (such as 2G, GSM, 3G,WCDMA, CDMA, LTE, WLAN, Wi-Fi), mobile backhaul network, or core networksuch as IMS, CS Core, PS Core.

Within the context of the present application, the term radio basestation refers to a node of a radio access network that is used asinterface between land-based transport links and radio based transportlinks, wherein the radio based transport link interfaces directly a userequipment. For example, in a GSM/2G access network a radio base stationrefers to a BTS, in a WCDMA/3G access network a radio base stationrefers to a NodeB, and in a LTE access network a radio base stationrefers to a eNodeB. In a WLAN/Wi-Fi architecture a radio base stationrefers to an Access Point (AP).

Referring to FIG. 1, this figure shows a diagram illustrating a systemfor providing coverage of a wireless communication network according tothe invention.

In this embodiment a targeted radio coverage area 140 is realized by aplurality of radio coverage sub-areas 130. The radio coverage sub-areas130 are provided by radio base stations 150 mounted on mobile robots100. In this embodiment the mobile robots 100 are unmanned aerialvehicles, also known as drones. A plurality of user equipment 120 areroaming in the radio coverage area 140 and are radio attached to theradio coverage sub-areas 130 provided by radio base stations 150 mountedon mobile robots 100. Furthermore, there is a maintenance base 110located within the radio coverage area 140 or located close to it. Themaintenance base 110 comprises a plurality of mobile robots 100 forinitial deployment or as spare mobile robots 100 for deployment in caseof failure of one of the deployed mobile robots 100.

In an alternative embodiment there may be more than one maintenance base110 being allocated to the radio coverage area 140. This may be the caseif the radio coverage area 140 is very large and the mobile robots 100would have to travel long distances to their deployment position. Alsofor redundancy purposes it would be beneficial to use a more than onemaintenance base 110. If for example the radio coverage area 140 wouldcover an earthquake disaster area, then due to the possibility offurther earthquakes in the same area a further maintenance base 110could act as stand-in in case of damages to the first maintenance base110.

It may also be possible that a single maintenance base 110 could servemore than one radio coverage area 140. For example it the radio coverageareas 140 are small but located close to each other, a singlemaintenance base 110 could be placed in equal distance to both radiocoverage areas 140 and the single maintenance base 110 could serve bothradio coverage areas 140.

A maintenance base 110 also comprises equipment needed to performmaintenance or repair tasks on mobile robots 100. A regular maintenancetask would be to recharge or refuel mobile robots 100, so themaintenance base 110 could comprise fuel storage and/or electricity gridconnections. Mobile robots 100 consume energy when moving from oneposition to a further position. In the example of drones, energy isconsumed even if without movement. Energy would be needed for hoveringat a given position at a constant altitude. On the other hand, dronesmay also land on exposed positions for providing their radio coveragesub-area 130, and by this reducing the energy consumption. However,energy would still be needed for powering the mounted radio base station150 and for powering other electric parts needed for operation such astransceiver, handover controller, positioning unit, or operation statusdetermination unit (see FIG. 12). The maintenance base 110 could inaddition comprise spare parts needed for repairing failed mobile robots100.

The maintenance base 110 may operate stand-alone or may be connected toor associated with for example an operation and maintenance center ofthe wireless communication network. In this case the maintenance base110 may receive input from the wireless communication network on thetargeted radio coverage area 140, so for example a coverage range, acoverage shape, or a capacity demand at specific geographical positions.The maintenance base 110 may also report back to the wirelesscommunication network on the status of the provided radio coverage area140.

The mobile robots 100 may be capable of communicating with themaintenance base 110. This communication link may be bidirectional andis used to transmit instructions from the maintenance base 110 to themobile robots 100. The other direction may be used by the mobile robots100 to report their operational status to the maintenance base 110. Themaintenance base 110 may also use the communication link to performtriangulation and by that determine or verify the geographical position200 of the mobile robots 100.

This communicating may be achieved via a direct radio or optical linkfrom each mobile robot 100 to the maintenance base 110 with the help ofdirected/rotatable radio antenna, laser (using different colors, orinfrared) or maser. The communication may also be routed via one orseveral satellite hops (geostationary or low orbit satellites), or viaother land based hops to the maintenance base 110. The communication mayalso be forwarded through one or several other mobile robots 100functioning as relay points for the communication. One or several mobilerobots 100 may hover at a higher altitude and operate as central relayhop for the entire communication towards the maintenance base 110.Depending on the type of ground, such relay point mobile robots 100 mayalso operate at a lower altitude, for example in narrow valleys inmountain areas, or in urban corridors of streets or rail tracks. Badweather conditions may also force to choose a lower altitude for relaypoint mobile robots 100.

The radio base stations 150 are mounted on mobile robots 100, so eachmobile robot 100 may carry one radio base station 150. By alternative,there may be more than one radio base station 150 per mobile robot 100,or there may be specialized mobile robots without radio base stationacting as communication hub only. The radio base stations 150 areconnected to the access network of the wireless communication network.This connection may be realized via the communication link of the mobilerobots 100 to the maintenance base 110, or may also utilize a separateradio link or optical link. So the wireless communication network doesnot see any differences whether a radio base station 150 is mounted on amobile robot 100 or a radio base station is land-based.

In an alternative embodiment a mobile robot 100 may carry more equipmentof the wireless communication network than just a radio base station150. A mobile robot 100 may be adapted to comprise in addition oralternatively to the radio base station 150 also at least one of thefollowing wireless communication network elements: Serving GPRS SupportNode (SGSN), Mobility Management Entity (MME), Gateway GPRS Support Node(GGSN), Mobile Switching Center (MSC), Gateway MSC (GMSC), Media Gateway(MGW), and Radio Access Network Controller. Hosting these additionalwireless communication network elements may allow calls and/or packetsessions between two user equipments 120 in the same area covered by onemobile robot 100 to be handled locally within the mobile robot 100 andby this minimizing any interaction with other land-based elements of thewireless communication network.

FIG. 1 shows a static scenario when mobile robots 100 have been deployedand the targeted radio coverage area 140 has been established. In orderto reach this state, mobile robots 100 need to be initially deployed,mobile robots 100 need to be replaced for maintenance purposes, andunexpectedly failing mobile robots 100 have to be replaced in anefficient way, minimizing effects on the provisioning of the radiocoverage area 140. In addition, it may be necessary to stop theprovisioning of the radio coverage area 140, when the need for the radiocoverage area 140 has ceased. These steps are explained with the help ofthe following figures.

Referring to FIG. 2, this figure shows an illustration of mobile robotstaking up geographical positions from the maintenance base, according tothe invention.

The figure shows details of the initial deployment of mobile robots 100.In a first step the radio coverage area 140 to be provided by the radiobase stations 150 mounted on said mobile robots 100 has to bedetermined. The maintenance base 110 may determine the targeted radiocoverage area 140 on its own (corresponding data may have been providedto the maintenance base 110 directly), or receive this data as inputfrom for example an operation and maintenance center of the wirelesscommunication network. Input data may be the range of the radio coveragearea 140, the shape and the capacity demands at certain locations.

After the targeted radio coverage area 140 has been determined, themaintenance base 110 determines geographical positions 200 for themobile robots 100. These geographical positions 200 are determined in away that they are suitable to provide the targeted radio coverage area140. A mobile robot 100 deployed at a geographical position 200 provideswith the help of its mounted radio base station 150 a radio coveragesub-area 130, and the plurality of radio coverage sub-area 130 make upthe targeted radio coverage area 140. So the geographical positions 200are determined to meet the input data coverage range, coverage shape,and capacity. The radio coverage sub-areas 130 may overlap with eachother, may form a seamless coverage area, or may leave uncovered areasin-between them.

The maintenance base 110 then deploys mobile robots 100 at thedetermined geographical positions 200 by instructing them to take uptheir determined geographical positions 200.

A mobile robot 100 located at or in the maintenance base 110 receivingsuch instruction then moves to the instructed geographical positions200.

The figure shows a scenario where five geographical positions 200labeled A to E have been determined. Three of these five geographicalpositions 200, positions A, B, and C have been deployed already withmobile robots 100. The remaining two geographical positions 200 D and Eare still vacant and need to be deployed with further mobile robots 100.So as a next step the maintenance base 110 instructs one further mobilerobot 100 to take up the geographical position D, and then anothermobile robot 100 to take up the geographical position E. After that allgeographical positions 200 are deployed with mobile robots 100.

The mobile robots 100 may be instructed by the maintenance base 110 totake up their geographical positions 200 by moving straight from themaintenance base 110 to their determined geographical positions 200. Themobile robots 100 may be also be instructed by the maintenance base 110to follow a given path for deployment.

Referring to FIG. 3, this figure shows an illustration of a daisy chainloop of deployed mobile robots, and a circular shift operation,according to the invention.

At this point all geographical positions 200 have been deployed withmobile robots 100. The next step is to prepare the replacement of adeployed mobile robot 100 in order to maintain the radio coverage area140. The deployed mobile robots 100 consume energy and need to berecharged/refuel at periodic intervals. Also other periodic maintenancetasks need to be performed on the mobile robots 100 in order to ensuresmooth operation. For this purpose a plan is needed to move all deployedmobile robots 100 back to the maintenance base 110 after a certainperiod of operation.

In this embodiment the solution is to instruct a deployed mobile robot100 to be replaced to return to the maintenance base 110 and to deploy afurther mobile robot 100 to a vacant geographical position 200. Afterthe deployed mobile robot 100 to be replaced has left his geographicalposition 200, a new mobile robot 100 may be instructed to take up thisvacant geographical position 200. So for example in the figure themobile robot 100 on geographical position 200 C returns to themaintenance base 110 and the maintenance base 110 instructs a furthermobile robot 100 to move from the maintenance base 110 to the vacantgeographical position 200 C.

By alternative, the maintenance base 110 may re-arrange the deploymentof mobile robots 100 to geographical positions 200 before instructing afurther mobile robot 100 to start from the maintenance base 110. Forthis re-arrangement the maintenance base 110 instruct one or severaldeployed mobile robot 100 to move from their current geographicalposition 200 to a vacant geographical position 200 and by thisre-arrange the deployment of mobile robots 100 to geographical positions200. After the re-arrangement still one vacant geographical position 200remains which is then filled on instruction by the maintenance base 110with a newly deployed mobile robot 100. After that all geographicalpositions 200 are filled again with mobile robots 100 and the radiocoverage area 140 is maintained.

In this embodiment the re-arranging the deployment of mobile robots 100to geographical positions 200 is done in a structured way. For this adaisy chain loop 300 of deployed mobile robots 100 is determined,wherein the maintenance base 110 is allocated to the daisy chain loop300 as an entry/exit element.

The figure shows an example of a determined daisy chain loop 300consisting of mobile robots 100 deployed at the geographical positions200 A to E and the maintenance base 110. The determination of the daisychain loop 300 and the allocation of mobile robots 100 to the daisychain loop 300 may be performed by the maintenance base 110.

The above described step of re-arranging the deployment of mobile robots100 to geographical positions 200 is done by utilizing the ringstructure of the daisy chain loop 300. The mobile robots 100 of thedaisy chain loop 300 perform a circular shift operation within the daisychain loop 300, wherein the last mobile robot 100 of the daisy chainloop 300 is returning to the maintenance base 110, and a further mobilerobot 100 is deployed to a vacant first position of the daisy chain loop300.

This circular shift operation within the daisy chain loop 300 is shownin the figure. So the mobile robot 100 deployed at geographical position200 E is instructed to move back to the maintenance base 110. The nowvacant geographical position 200 E is then filled by instructing themobile robot 100 deployed at geographical position 200 D to move to thegeographical position 200 E and by this leaving geographical position200 D vacant. This shift operation is continued along the daisy chainloop 300 until geographical position 200 A is left vacant. This vacantgeographical position 200 A is then filled with a new mobile robot 100from the maintenance base 110.

So the circular shift operation within the daisy chain loop 300 makesthe mobile robots 100 allocated to the daisy chain loop 300 to movearound the loop and by that achieve a re-arranging the deployment ofmobile robots 100 to geographical positions 200. At the same time themobile robot 100 of the geographical position 200 A is replaced by a newmobile robot 100 from the maintenance base 110 entering the daisy chainloop 300 at geographical position 200 A. A mobile robot 100 returning tothe maintenance base 110 will then be for example recharged/refueled andcan then at the next circular shift operation within the daisy chainloop 300 be fed again into the daisy chain loop 300 at position A.

The circular shape of the daisy chain loop 300 in the figure is to beseen as a logical abstraction of a real shape of the daisy chain loop300. The real shape may depend for example on geographical obstaclesthat need to be avoided when moving from one geographical position 200to the next geographical position 200 of the daisy chain loop 300. Themobile robots 100 may also move along a shortest path betweengeographical positions 200 of the daisy chain loop 300, causing a realdaisy chain loop 300 to have a non-circular shape.

The daisy chain loop 300 may also be utilized at initial deployment ofmobile robots 100. In this case the determination of the daisy chainloop 300 is done before the initial deployment is initiated. Mobilerobots 100 may be instructed by the maintenance base 110 to take uptheir geographical positions 200 by moving along a path of the daisychain loop 300 starting from the maintenance base 110.

The mobile robots 100 may take up the geographical position 200 and/ormay return to the maintenance base 110 by moving along a given path. Themaintenance base 110 may instruct this path to the mobile robots 100.

The structured re-arranging the deployment of the mobile robots 100 togeographical positions 200 along the daisy chain loop 300 allows amobile robot 100 to return to the maintenance base 110 at periodicintervals for maintenance. The time a mobile robot 100 can operate maydepend on several factors. This embodiment takes those factors intoaccount when determining the number of daisy chain loop 300 elements. Soin the figure the daisy chain loop 300 consists of five elements.

The number of daisy chain loop 300 elements may be determined takingmovability of the mobile robots 100 into account. Movability of themobile robots 100 may be related to at least one of, a moving speed, areaching range, a regular maintenance interval and arecharging/refueling interval. The number of daisy chain loop 300elements may also be related to at least one of: a size of the radiocoverage area 140 generated by the radio base stations 150 mounted onmobile robots 100, a shape of the coverage area of the wirelesscommunication network, a capacity of the coverage area of the wirelesscommunication network, and a maximum payload of the mobile robots 100.

In addition to the number of daisy chain loop 300 elements, a furthercriterion for the time until a deployed mobile robot 100 returns to themaintenance base 110 may be at what intervals the circular shiftoperation is triggered. If the circular shift operation is periodicallytriggered after short intervals the mobile robots 100 will return soonerto the maintenance base 110. So by adjusting the trigger interval of thecircular shift operation a timely return of the mobile robots 100 to themaintenance base 110 can be achieved.

The circular shift operation within the daisy chain loop 300 may betriggered in periodic intervals by the maintenance base 110. Theperiodic interval may be determined such that the mobile robots 100 ofthe daisy chain loop 300 are shifted to the maintenance base 110 bycircular shift operations before reaching a critical operational status.A critical operational status may be reached if a mobile robot 100 runsout of energy or if the mobile robot 100 requires periodic maintenance.

The circular shift operation may be performed clock-wise or counterclock-wise and may be decided by the maintenance base 110.

In addition or by alternative the circular shift operation within thedaisy chain loop 300 may be triggered by one of the mobile robots 100 ofthe daisy chain loop 300. A mobile robot 100 of the daisy chain loop 300may detect that a return to the maintenance base 110 is needed earlierthan originally planned or calculated at departure from the maintenancebase 110. The reason for that may for example be that moving across theterrain required more energy than anticipated at departure from themaintenance base 110. In this case the mobile robot 100 may inform themaintenance base 110 and the maintenance base 110 may instruct anadditional circular shift operation or shorten the time interval betweenthe circular shift operations and by that ensuring that the mobile robot100 returns to the maintenance base 110 before a critical operationstatus is reached. By alternative, a mobile robot 100 may trigger thecircular shift operation directly by contacting the other mobile robots100 of the daisy chain loop 300.

In an alternative embodiment the mobile robots 100 may perform thecircular shift operation by permanently moving from a currentgeographical position 200 to a further geographical position 200 of thedaisy chain loop 300. By performing a slow movement the mobile robots100 may lower the energy consumption. This may be the case if forexample a mobile robot 100 is not able to hover at a geographicalposition 200 but has to stay in movement it order to gain uplift. Thecircular shift operation may then be realized by a permanent slowmovement of the mobile robots 100 along the daisy chain loop 300.

When the provisioning of the coverage of the wireless communicationnetwork is to be stopped, the maintenance base 110 recalls all deployedmobile robots 100. A mobile robot 100 being instructed to return to themaintenance base 110 may switch off its mounted radio base station andby this closes down the related radio coverage sub-area 130 beforemoving back to the maintenance base 110. The maintenance base 110 mayinstruct the mobile robots 100 one by one to return to the maintenancebase 110. By alternative, the maintenance base 110 may instruct circularshift operations without feeding in new mobile robots 100 into the daisychain loop 300 and by that bring all mobile robots 100 back to themaintenance base 110. The maintenance base 110 may also instruct themobile robots 100 to return to the maintenance base 110 and the mobilerobots 100 will by themselves select a return path along the daisy chainloop 300. This controlled shut-down of the radio coverage area 140avoids jams of returning mobile robots 100 at the maintenance base 110.

The maintenance base 110 may decide to only shut down parts of the radiocoverage area 140 and leave the rest operative. The maintenance base 110may then also change the assignment of deployed mobile robots 100 todaisy chain loops 300.

A user equipment 120 camping in the radio coverage area 140 provided bythe radio base stations 150 mounted on the mobile robots 100 does notrecognize whether its radio attachment is towards a land based radiobase station or a mobile robot 100 mounted radio base station 150. Theuser equipment 120 selects the strongest radio for attachment.

A user equipment 120 may perform a change of radio attachment when thedeployed mobile robots 100 are re-arranged or replaced, if the userequipment 120 is camping in the radio coverage area 140 provided by theradio base stations 150 mounted on the mobile robots 100. When mobilerobots 100 move to new geographical positions 200 due to re-arrangementor circular shift operation, they may continue to provide theirrespective radio coverage sub-area 130. For a user equipment 120 this isvisible by a decreasing radio strength of the radio coverage sub-area130 the UE is attached to, as the respective mobile robot 100 is movingaway. At the same time a new mobile robot 100 is approaching whichcauses the user equipment 120 to detect a new radio coverage sub-area130 provided by the new approaching mobile robot 100. When reaching alower radio strength threshold, the user equipment 120 may switch itsradio attachment to the radio coverage sub-area 130 provided by thenewly approaching mobile robot 100.

For a circuit switched attached user equipment 120 the change of theradio attachment may cause the user equipment 120 to perform a locationupdate procedure. For a packet switched attached user equipment 120 thechange of the radio attachment may cause the user equipment 120 toperform a tracking or routing area update procedure.

If a mobile robot 100 has to be replaced all the ongoing calls and/orpacket sessions that are currently handled by the radio base station 150mounted on the mobile robot 100 to be replaced have to be continued, sohanded over to a new radio base station 150 mounted on a new mobilerobot 100. The maintenance base 110 may send an instruction to a mobilerobot 100 for handing over a handling of ongoing calls and/or packetsessions from the mobile robot 100 to a further mobile robot.

A mobile robot 100 may receive an instruction from the maintenance base110 for handing over the handling of ongoing calls and/or packetsessions. In an alternative embodiment the mobile robot 100 may triggerhanding over the handling of ongoing calls and/or packet sessions basedon a detected proximity of a further mobile robot 100. In this case themaintenance base 110 may have instructed a new mobile robot 100 to takeup the geographical position 200 of the mobile robot 100 to be replaced.When the mobile robot 100 to be replaced detects that a new mobile robot100 is approaching the own geographical position 200 and comes closerthan a lower threshold, the hand-over is triggered.

In an alternative embodiment the handing over the handling of ongoingcalls and/or packet sessions may be done by fading the radio strength ofthe provided radio coverage area 140 or sub-area 130 and at the sametime increasing the radio strength of the radio coverage area 140 orsub-area 130 provided by the further mobile robot, causing at least oneuser equipment 120 to perform a change of a radio attachment and/orhandover. In this scenario a new mobile robot 100 is approaching thegeographical position 200 of the mobile robot 100 to be replaced. Whenboth mobile robot 100 are close to each other, the mobile robot 100 tobe replaced starts to fade the own radio strength generated by the ownradio base station 150. In parallel to this the new mobile robot 100starts to increase the radio strength generated by its own radio basestation 150. This causes a user equipment 120 attached to the fadingradio base station 150 to handover to the new radio base station 150.The need for this handover is detected and triggered by the accessnetwork of the wireless communication network and uses the well-knownprocedures for handover.

In order for a user equipment 120 to complete a handover procedurecorrectly, it is important that the handover is started timely, so thatthe wireless communication network has sufficient time to prepare thehandover. The handover command can be conveyed to the user equipment 120while it is still in coverage of the source radio coverage sub-area 130.For the user equipment 120 to be able to synchronize with the targetradio coverage sub-area 130 when executing the received handovercommand, the user equipment 120 needs to be in coverage of the targetradio coverage sub-area 130.

In case of radio base station 150 mounted on mobile robots 100, coverageto both source and target radio coverage sub-area 130 may not beavailable at the same time or only be available for a short time. Thehandover needs to be prepared from the wireless communication network atthe right time. Furthermore, it is important that the source accessnetwork sends the handover command to the right instance. Thesedecisions may be based on:

-   -   Speed of source mobile robot 100, target mobile robot 100, or        relative speed of both    -   Movement trajectory or forecasted estimate thereof, of source        mobile robot 100, target mobile robot 100, or both    -   Distances between source mobile robot 100, target mobile robot        100 and a user equipment 120    -   Altitude of source mobile robot 100, target mobile robot 100, or        relative to each other    -   Location of user equipment 120, source mobile robot 100 or        target mobile robot 100    -   Estimate of coverage of source mobile robot 100, target mobile        robot 100, or both, e.g. based on the criteria above

Furthermore, also user equipment 120 measurement reports can be utilizedto indicate that handover is imminent. Based on the criteria listedabove, the measurement report configuration of the user equipment 120may be adapted. In a particular embodiment, handover measurement eventthresholds, such as A3 threshold (measurement reports may be triggeredby a so called A3 event: A neighbor cell is found to be an offset betterthan the current serving cell. It should be noted that there aremultiple events that can trigger a measurement report), TTT (time totrigger) and CIO (cell individual offset) may be adjusted based on thecriteria above. For example, in case of high relative mobile robot 100speed, the TTT of the handover measurement event shall be low. Anotherexample is to apply low A3 threshold or CIO for the target mobile robot100 in this case.

In another embodiment, the user equipment 120 may apply the measuresdescribed above based on the criteria above in an autonomous way. Inparticular the user equipment 120 may scale/adjust the handovermeasurement parameters such as TTT, A3, CIO of the source or targetradio coverage sub-area 130, based on observed or estimated relativespeed of source mobile robot 100 and target mobile robot 100.

Moreover, a handover measurement report received from a user equipment120 connected to the source mobile robot 100 indicating radio coverageto the target mobile robot 100 could be used, e.g. in combination withcriteria above, to start a “mass handover procedure” in order tohandover multiple/all user equipment 120 from the source mobile robot100 to the target mobile robot 100. This may accelerate the handoverprocedure for all involved user equipment 120.

A deployed mobile robot 100 may send operational status reportsperiodically or on demand if the mobile robot 100 determines a criticaloperational status. The maintenance base 110 receiving operationalstatus reports from the deployed may use the operational status reportsto determine if a mobile robot 100 is in a critical operational status.The maintenance base 110 may also perform calculations in order toprediction whether a mobile robot 100 may reach a critical operationalstatus before it returns to the maintenance base 110 by circular shiftoperation at the current trigger interval for the circular shiftoperation. If the maintenance base 110 determines a critical operationalstatus, it may instruct the mobile robot 100 to return to themaintenance base 110. An operational status may comprise at least one ofa maintenance need of the mobile robot 100, and recharging/refuelingneed of the mobile robot 100.

Referring to FIG. 4, this figure shows an illustration of a plurality ofdaisy chain loops, all together forming a mobile coverage area,according to the invention.

In the previous figure a single daisy chain loop 300 was shown and themobile robots 100 were allocated to this single daisy chain loop 300only. This may be a viable approach if the targeted radio coverage area140 is rather small and/or has a simple shape. If a larger region has tobe covered, it may not be possible to allocate all required mobilerobots 100 to a single daisy chain loop 300. Such single daisy chainloop 300 would become too long and mobile robots 100 would not be ableto return in time to the maintenance base 110 for maintenance.

In an alternative embodiment a plurality of daisy chain loops 300 may beused. So the deployed mobile robots 100 may be distributed to aplurality of different daisy chain loops 300, wherein each deployedmobile robot 100 may be uniquely allocated to a single daisy chain loop300.

FIG. 4 shows a more complex scenario where the deployed mobile robots100, placed at various geographical positions 200, are allocated to fivedifferent daisy chain loops 300 A to E. Those daisy chain loops 300 mayhave non-circular shape and their shape may be adjusted to the needs ofthe targeted radio coverage area 140. For example the target may be toachieve radio coverage over land while leaving out sea or inland waterareas. In this case the shape of a daisy chain loop 300 may follow theshape of the land. Or the coverage area shall cover important streets orhighways interconnecting cities. In this case the shape of a daisy chainloop 300 may follow the path of the street, or several streets.

Each of those five different daisy chain loops 300 A to E follow theprinciples of the single daisy chain loop 300 as described in FIG. 3above. So a new mobile robot 100 is fed into a daisy chain loop 300 at acircular shift operation of the daisy chain loop 300, and the lastmobile robot 100 on the daisy chain loop 300 is returning to themaintenance base 110. The direction of the circular shift operation isindicated by the solid arrows in the figure. Both directions would bepossible to use, also in a mixture. So some daisy chain loops 300 mayshift right, other may shift left within the daisy chain loop 300.

In this embodiment with a plurality of daisy chain loops 300 themaintenance base 110 has to permanently provide new mobile robots 100 inorder to feed them into the five daisy chain loops 300 at circular shiftoperations. For this purpose the maintenance base 110 launchescontinuously new mobile robots 100 on a deployment track 400, indicatedby the dotted arrows starting off from the maintenance base 110. Thisdeployment track 400 can be seen as a feeder for the different daisychain loops 300. A new mobile robot 100 may start off from themaintenance base 110 and move along the deployment track 400. Themaintenance base 110 then decides on and instructs appropriate mobilerobots 100 on the deployment track 400 close to the entry geographicalpositions 200 into the different daisy chain loops 300 that a mobilerobot 100 shall leave the deployment track 400 and enter into one of thedaisy chain loops 300.

Referring to FIG. 5, this figure shows an illustration of a double daisychain loop, according to the invention.

The previous figures have shown an embodiment where mobile robots 100are deployed to geographical positions 200. Having taken up theinstructed geographical positions 200, the mobile robots 100 start toprovide radio coverage sub-areas 130 making up the entire radio coveragearea 140. At a circular shift operation a mobile robot 100 moves fromone geographical position 200 to a next geographical position 200. In apreviously described embodiment the mobile robots 100 continue toprovide their radio coverage sub-area 130 while being shifted around.This has the disadvantage that the radio coverage sub-areas 130 are alsomoving around along the daisy chain loop 300.

In an alternative embodiment this drawback is eliminated by keeping aradio coverage sub-area 130 always tied to a geographical position 200.As a consequence mobile robots 100 may have to be reconfigured for usein a new geographical position 200 while on the move from a previousgeographical position 200 to the new geographical position 200. Inparticular the radio base stations 150 mounted on the mobile robots 100have to be tuned to provide the radio coverage sub-area 130 of that newgeographical position 200.

Since this reconfiguration may take some time and may involvedownloading or exchange of configuration information, this alternativeembodiment uses a concept of a double daisy chain loop as shown in FIG.5.

The figure shows four geographical positions 200 A to D, on each ofthese geographical positions 200 a mobile robot 100 is deployedproviding the radio coverage sub-area 130 of the geographical positions200 A to D. The geographical positions 200 A to D are allocated to adaisy chain loop 300 that chains up the deployed mobile robots 100.

In-between the geographical positions 200 A and B, B and C, and C and D,spare mobile robots 100 are positioned on a parallel daisy chain loop,here named as X, Y, and Z. These in-between mobile robots 100 do notgenerate any radio coverage sub-area 130, but their mounted radio basestations 150 are inactivated and are being reconfigured while beinglocated at this in-between position.

In a circular shift operation on a previously described daisy chain loop300, mobile robot 100 A would move to geographical positions 200 B.However, in a circular shift operation done in this double daisy chainloop, mobile robot 100 A now moves into the in-between position X andgoes inactive for reconfiguration. At the same time mobile robot 100 Xmoves into the geographical positions 200 B and starts to generate theradio coverage sub-area 130 for this geographical position 200, and soon. So all active mobile robots 100 move into in-between positions andperform reconfiguration. All mobile robots 100 on in-between positionsmove to geographical positions 200 and go active with their newconfiguration.

So one half of the mobile robots 100 is passive and reconfiguring, whilethe other half is active and provide radio coverage sub-area 130. Bothhalves can be allocated to two parallel daisy chain loops, also calleddouble daisy chain loop. The two daisy chain loops of the double daisychain loop may perform circular shifts in the same direction or may alsoperform shifts in opposite directions. In FIG. 5 this would mean thatfor example that mobile robots 100 X, Y, Z being allocated to a firstdaisy chain loop are shifting to the right, while mobile robots 100 A,B, C, D being allocated to a second daisy chain loop are shifting to theleft.

Referring to FIG. 6, this figure shows an illustration of a replacementof a failing mobile robot from a deployment buffer, according to theinvention.

It may happen that a deployed mobile robot 100 fails unexpectedly. Itmay have been destroyed at a natural disaster or by human interaction,or may fail due to a malfunction of the mobile robot 100 itself or ofthe mounted radio base station 150. In this case the provisioning of theradio coverage sub-area 130 of the failed mobile robot 600 is suddenlyterminated. In order to maintain targeted the radio coverage area 140,the failed mobile robot 600 need to be replaced as soon as possible.

FIG. 6 shows an embodiment where a failed mobile robot 600 is replacedwith minimal delay. Five mobile robots 100 are deployed to fivegeographical positions 200 and this figure assumes that the middlemobile robot 600 has failed. The five mobile robots 100 are allocated toa daisy chain loop 300.

The maintenance base 110 then determines the failure of the middlemobile robot 600. The maintenance base 110 may determine failure if noperiodic status reports are received from a mobile robot 100 in time, bysupervision with a heartbeat message or by periodic polling of thestatus of the mobile robots 100. Depending on the type of fault, thefailed mobile robot 600 may even be capable of sending a failureindication to the maintenance base 110 before going out of service.

Having determined the failure of the middle mobile robot 600, themaintenance base 110 instructs the mobile robots 100 of the daisy chainloop 300, being placed in the daisy chain loop 300 before the failingmobile robot 600, to perform a circular shift operation. This circularshift operation causes the mobile robot 100 A next to the failed mobilerobot 600 to fill in the geographical position 200 of the failed mobilerobot 600. It can be assumed that the mobile robot 100 A is locatedclose to the failed mobile robot 600, and therefore can quickly takeover.

Having performed this partial circular shift operation leaves the firstgeographical position 200 of the daisy chain loop 300 vacant and a newmobile robot 100 needs to be deployed from the maintenance base 110. Inthis embodiment, the maintenance base 110 runs a deployment buffer 610of mobile robots 100. So the maintenance base 110 has launched at leastone spare mobile robot 100, which is then waiting for immediatedeployment at a centrally located waiting position. For flying mobilerobots this may be done by letting the mobile robot 100 circulate overthe maintenance base 110 (or any other central position) in order to beavailable for immediate deployment at failure cases. If a mobile robot100 is removed from the deployment buffer 610 and deployed to a daisychain loop 300, the maintenance base 110 launches a new mobile robot 100to re-fill the deployment buffer 610. The radio base stations 150mounted on mobile robots 100 in the deployment buffer are still inactiveand would be configured and activated at deployment.

If a geographical position 200 of a failed mobile robot 600 is not toofar away, it may alternatively be possible to replace the failed mobilerobot 600 directly with a new mobile robot 100 from the deploymentbuffer 610. In this case the replacement mobile robot 100 can beconfigured to the failed radio coverage sub-area 130 at thatgeographical position 200 while being on the move to the deploymentgeographical position 200.

Mobile robots 100 may circulate in the deployment buffer 610 for sometime and then return to the maintenance base 110 forrecharging/refueling. The maintenance base 110 may also use thedeployment buffer 610 as a deployment track 400 as described in FIG. 4.However, the maintenance base 110 has to ensure that the deploymentbuffer 610 is always well filled with “fresh” mobile robots 100 that canimmediately be used for replacement of failing mobile robots 600.

Referring to FIG. 7, this figure shows a first flow diagram in a mobilerobot, according to the invention. This flow describes a deployment,provisioning, returning cycle of a mobile robot 100.

The mobile robot 100 may receive in step 700 an instruction to take up ageographical position 200. This instruction may be received from themaintenance base 110 and the mobile robot 100 receiving this instructionmay be placed in or close to the maintenance base 110. This may be aninitial deployment of this mobile robot 100, or the mobile robot 100 mayhave been returning to the maintenance base 110 before, and is sent backinto deployment after refueling/recharging and regular maintenance.

In step 710 the mobile robot 100 may then take up the indicatedgeographical position 200. The mobile robot 100 may take up theindicated geographical position 200 by moving straight from themaintenance base 110 to the indicated geographical position 200. Byalternative the mobile robot 100 may take up the indicated geographicalposition 200 by moving along a path of the daisy chain loop 300 startingfrom the maintenance base 110. By alternative the mobile robot 100 maytake up the indicated geographical position 200 by moving along a givenpath, wherein the path may be instructed by the maintenance base 110.Having reached the indicated geographical position 200, the mobile robot100 may hover at that indicated geographical position 200, land on theground or at an exposed position, circle around that indicatedgeographical position 200 or simply stay there depending on the type ofmobile robot 100.

In step 720 the mobile robot 100 may provide a radio coverage sub-area130 at the geographical position 200. The plurality of all providedradio coverage sub-areas 130 make up the entire radio coverage area 140.The mobile robot 100 uses the mounted radio base station 150 forprovisioning the radio coverage sub-area 130.

In the next step the mobile robot 100 waits for further instructions,for example from the maintenance base 110. If the further instruction isa command to return to the maintenance base 110, step 760 is executed.If the further instruction is a command to move to a newly indicatedgeographical position 200, step 740 is executed.

Step 740 is executed if the mobile robot 100 receives an instruction tomove to a new geographical position 200. In this step the mobile robot100 may continue to provide the radio coverage sub-area 130 while movingin step 750 to the newly indicated geographical position 200. The flowthen loops back and the mobile robot 100 continues in step 730 withwaiting for new instructions. This flow shows an embodiment where themobile robot 100 continues to provide the radio coverage sub-area 130while moving new geographical position 200. Alternative embodiments aredescribed above where the mobile robot 100 discontinues to provide theradio coverage sub-area 130, re-configures, and provides another radiocoverage sub-area 130 at the target geographical position 200.

Step 760 is executed if the mobile robot 100 receives an instruction toreturn to the maintenance base 110. In this case the mobile robot 100stops to provide the radio coverage sub-area 130 and returns in step 770to the maintenance base 110. Then the flow ends. By alternative themobile robot 100 may be instructed to return to some other collectionpoint where mobile robots 100 are gathered.

Referring to FIG. 8, this figure shows a second flow diagram in a mobilerobot, according to the invention. This flow describes the return of amobile robot 100 at a critical operational status.

The flow starts when in step 800 the mobile robot 100 determines its ownoperational status. The mobile robot 100 may determine its ownoperational status in periodic intervals. By alternative or in addition,the mobile robot 100 may determine its own operational status oninstruction from the maintenance base 110. By alternative or inaddition, the mobile robot 100 may determine its own operational statusin case the mobile robot 100 detects some malfunction.

In step 810 the mobile robot 100 analyzes the own operational status anddetermines whether the own operational status is critical. A criticaloperational status may for example be if the mobile robot 100 detects anurgent maintenance need or if recharging/refueling is required. If nocritical operational status is detected, the flow may end immediately.By alternative or in addition, the mobile robot 100 may send in periodicintervals operational status reports to the maintenance base 110. Thoseperiodic operational status reports may also indicate to the maintenancebase 110 that the mobile robot 100 is operating well and no faults havebeen detected. So even if no critical operational status has beendetected, the mobile robot 100 may send an operational status reports tothe maintenance base 110 if sending of a periodic operational statusreport is due.

If a critical operational status is detected by the mobile robot 100,the mobile robot 100 sends immediately in step 820 a status report tothe maintenance base 110 comprising the operation status of the mobilerobot 100. The operation status may comprise a maintenance need of themobile robot 100, and/or a recharging/refueling need of the mobile robot100.

Triggered by this status report the mobile robot 100 may receive aninstruction for handing over the handling of ongoing calls and/or packetsessions. In this case the mobile robot 100 shall hand-over the handlingof ongoing calls and/or packet sessions in the mounted radio basestation 150 to a further mobile robot 100. The mobile robot 100 hasstill to wait with the hand-over until a further mobile robot 100arrives.

In step 840 the mobile robot 100 then detects the proximity of a furthermobile robot 100. This further mobile robot 100 may have been instructedby the maintenance base 110 to move to the geographical position 200 ofthe mobile robot 100.

In step 850 the handling of ongoing calls and/or packet sessions arehanded-over to the further mobile robot 100. By alternative, the mobilerobot 100 may report the detection of the proximity of a further mobilerobot 100 to the maintenance base 110 and as a response the maintenancebase 110 may instruct the mobile robot 100 to hand-over handling ofongoing calls and/or packet sessions to the further mobile robot 100.

In step 860 the mobile robot 100 stops providing the radio coveragesub-area 130, for example by switching off the mounted radio basestation 150.

In step 870 the mobile robot 100 then returns to the maintenance base110. By alternative the mobile robot 100 may be instructed to return tosome other collection point where mobile robots 100 are gathered. Thenthe flow ends.

Referring to FIG. 9, this figure shows a first flow diagram in amaintenance base, according to the invention. This flow describes a fullprovisioning cycle of radio coverage.

The flow starts in step 900 with determination of a radio coverage area140 to be provided by the radio base stations 150 mounted on the mobilerobots 100. The targeted radio coverage area 140 may have been suppliedby an operation and maintenance center of the wireless communicationnetwork.

The maintenance base 110 may operate stand-alone or may be connected toor associated with for example an operation and maintenance center ofthe wireless communication network. In this case the maintenance base110 may receive input from the wireless communication network on thetargeted radio coverage area 140, so for example a coverage range, acoverage shape, or a capacity demand at specific geographical positions.The maintenance base 110 may also report back to the wirelesscommunication network on the status of the provided radio coverage area140.

Having determined the targeted radio coverage area 140, the maintenancebase 110 determines in step 910 geographical position 200 suitable forproviding the targeted radio coverage area 140. The targeted radiocoverage area 140 is made up by a plurality of radio coverage sub-areas130 provided by radio base stations 150 mounted on mobile robots 100. Sothe maintenance base 110 determines geographical position 200 such thatif mobile robots 100 are placed there, the plurality of radio coveragesub-areas 130 make up the targeted radio coverage area 140. For thedetermination the maintenance base 110 may consider the capabilities ofthe mobile robots 100 and their mounted radio base stations 150. Somemobile robots 100 may be have a stronger radio base station 150 mounted,capable of generating larger radio coverage sub-areas 130, or specificshaped radio coverage sub-areas 130, or even multiple radio coveragesub-areas 130 of smaller size.

In step 920 the maintenance base 110 deploys mobile robots 100 at thedetermined geographical position 200 suitable for providing the targetedradio coverage area 140. The maintenance base 110 may do this deploymentof mobile robots 100 by instructing each mobile robot 100 to take up aninstructed geographical position 200.

In step 930 the maintenance base 110 determines a daisy chain loop 300of deployed mobile robots 100 and the maintenance base 110. The daisychain loop 300 consists of deployed mobile robots 100, wherein themaintenance base 110 is allocated to the daisy chain loop 300 as anentry/exit element.

The number of daisy chain loop 300 elements may be determined takingmovability of the mobile robots 100 into account. Movability of themobile robots 100 may be related to at least one of, a moving speed, areaching range, a regular maintenance interval and arecharging/refueling interval. The number of daisy chain loop 300elements may also be related to at least one of: a size of the radiocoverage area 140 generated by the radio base stations 150 mounted onmobile robots 100, a shape of the coverage area of the wirelesscommunication network, a capacity of the coverage area of the wirelesscommunication network, and a maximum payload of the mobile robots 100.

By alternative, step 930 may be executed before step 920, so first thedaisy chain loop 300 is determined and then deployment of the mobilerobots 100 is done.

The maintenance base 110 may also determine multiple daisy chain loops300, all of them having the maintenance base 110 allocated as anentry/exit element.

In step 940 the maintenance base 110 determines a trigger interval for acircular shift operation within the daisy chain loop 300. In addition tothe number of daisy chain loop 300 elements, a further criterion for thetime until a deployed mobile robot 100 returns to the maintenance base110 may be at what interval the circular shift operation is triggered.If the circular shift operation is triggered at short intervals themobile robots 100 will return sooner to the maintenance base 110. So byadjusting the trigger interval of the circular shift operation a timelyreturn of the mobile robots 100 can be achieved.

In step 950 a circular shift operation is triggered within the daisychain loop 300, based on the determined periodical trigger interval. Forthis the maintenance base 110 instructs each mobile robot 100 of thedaisy chain loop 300 to move to a new geographical position 200. Thisinstruction may be sent out to all mobile robots 100 of the daisy chainloop 300 at the same time, or starting with the last mobile robot 100 ofthe daisy chain loop 300 first. So the last mobile robot 100 isinstructed to return to the maintenance base 110. The last but onemobile robot 100 is instructed to move to the now vacant last positionof the daisy chain loop 300. This shift is continued until the firstmobile robot 100 moves to the second position, leaving the firstposition vacant. The maintenance base 110 finally instructs a new mobilerobot 100 to take up the vacant first position of the daisy chain loop300.

In step 960 the maintenance base 110 checks if the provisioning of theradio coverage area 140 is to be stopped. If this is not the case, theflow is looping back to step 950.

The provisioning of the radio coverage area 140 may be stopped oninstruction of a operation and maintenance center, or may be stopped bythe maintenance base 110 based on usage time, targeted time of the day,usage information, lack of working mobile robots 100 or other reasons.The provisioning of the radio coverage area 140 may also be stopped onlypartly.

If the provisioning of the radio coverage area 140 is to be stopped instep 970 the maintenance base 110 recalls the deployed mobile robots 100to return to the maintenance base 110 or to return to some othercollection point where mobile robots 100 are gathered. Then the flowends.

Referring to FIG. 10, this figure shows a second flow diagram in amaintenance base, according to the invention. This flow describes thehandling of status reports and maintaining of the targeted radiocoverage area 140.

In step 1000 the maintenance base 110 receives a status report from adeployed mobile robot 100. The maintenance base 110 may receive periodicstatus reports from deployed mobile robots 100, or the maintenance base110 may receive status reports from deployed mobile robots 100 havingdetermined a critical operational status.

In step 1010 the maintenance base 110 determines the operational statusof the deployed mobile robot 100 sending the status report. Theoperational status may comprise information such as a maintenance needof the mobile robot 100, or a recharging/refueling need of the mobilerobot 100.

In step 1020 the maintenance base 110 determines whether the mobilerobot 100 is in a critical operational status. A critical operationalstatus may for example be if the mobile robot 100 detects an urgentmaintenance need or if recharging/refueling is required. If themaintenance base 110 determines no critical operational status of thesending mobile robot 100, the flow ends immediately. Alternatively themaintenance base 110 may log the content of the status report forstatistical and/or performance optimization purposes.

If the maintenance base 110 determines the operational status of thesending mobile robot 100 to be critical, step 1030 is performed. In thisstep the maintenance base 110 instructs the mobile robot 100 to returnto the maintenance base 110. However, the operational status of thesending mobile robot 100 may be very critical and the mobile robot 100may not be capable anymore to return to the maintenance base 110.

In the next step 1040 the maintenance base 110 re-arranges thedeployment of the mobile robots 100 to geographical positions 200. Themaintenance base 110 may perform this re-arrangement by instructing theremaining deployed mobile robots 100 to perform a circular shiftoperation within the daisy chain loop 300. The maintenance base 110 mayalso instruct only a part of the deployed mobile robots 100 to perform acircular shift operation (partly circular shift operation) and by thatclose a vacant position within the daisy chain loop 300.

In step 1050 the maintenance base 110 deploys a further mobile robot 100to a vacant geographical position 200. By alternative the step 1050 mayexecuted without previous re-arrangement in step 1040. Then the flowends.

Referring to FIG. 11, this figure shows a block diagram illustrating amobile robot, according to the invention. The illustrated entity maycorrespond to the mobile robot 100. The mobile robot 100 may be adaptedto perform one or more steps of the above described method shown in FIG.7 or FIG. 8.

The mobile robot 100 may comprise a number of functional units, whichare described in further detail below and which are adapted to performrespective method steps.

A processing unit 1100 of the mobile robot 100 may be adapted to processinstructions received from a maintenance base 110, to determine an ownoperational status to be critical, to determine a condition that areturn to the maintenance base 110 is required, to initiate handing overhandling of calls and/or packet sessions ongoing in the radio basestation 150 of the mobile robot 100 to a further mobile robot, or tocontrol the mounted radio base station 150. In a practicalimplementation the processing unit 1100 may be one processor taking careof all the above functions, or may also be distributed over more thanone processor, wherein the functions are distributed over the availableprocessors.

The mobile robot 100 may further comprise a sending unit 1102 and areceiving unit 1104 via which the mobile robot 100 can communicate withother entities of the wireless communication network such as the radioaccess network of the wireless communication network, the maintenancebase 110, or other mobile robots 100. The sending unit 1102 may send outsignaling messages composed by the processing unit 1100. The receivingunit 1104 may receive signaling messages originating from a radio accessnetwork of the wireless communication network, the maintenance base 110,or other mobile robots 100, and forward the received signaling messagesto the processing unit 1100 for processing. The mobile robot 100 maycomprise more than one sending unit and receiving unit for signalingcapacity and redundancy reasons.

The mobile robot 100 may also comprise one or several mounted radio basestations 150. A radio base station 150 is used to generate a radiocoverage sub-area 130. The radio base station 150 is used within theradio access network of the wireless communication network. The radiobase station 150 interfaces the processing unit 1100 in order to receiveinstructions, for example for re-configuration, initiation of hand-over,fading of radio strength, or shut-down.

The mobile robot 100 may also comprise a storing unit 1108 related tooperations for providing coverage of a wireless communication network.The storing unit 1108 may comprise various types of memory such asvolatile memory, non-volatile memory, hard disk drives, solid statedrives, a network interface to a database or a data center, securedigital cards, or hardware such as smart cards, non-reversible chips,security chips, security modules, or trusted platform module devices.The storing unit 1108 may be used by the processing unit 1100 forstoring information, for example program code.

The mobile robot 100 may also comprise a positioning unit 1110 fordetermination of the current position. This may for example be a GlobalPositioning System (GPS) receiver using satellites for positioning. Theprocessing unit 1100 may use the positioning information in order tocompare the current position with an instructed target position andusing the result to steer the movement controller 1116. The processingunit 1100 may use the positioning information in order maintain acurrent geographical position 200.

The mobile robot 100 may also comprise an operational statusdetermination unit 1112 for determining the own operational status. Theoperational status determination unit 1112 may for example comprisesensors to measure the amount of spare fuel or spare battery power. Theoperational status determination unit 1112 may also have timers or usagecounters to determine whether and when periodic maintenance is required.The information provided by the operational status determination unit1112 may be used by the processing unit 1100 to determine a criticaloperational status.

The mobile robot 100 may also comprise a handover controller 1114 forcontrolling a handover of handing over handling of calls and/or packetsessions ongoing in the radio base station 150 of the mobile robot 100to a further mobile robot. The handover controller 1114 does this byinteracting with the mounted radio base station 150.

The mobile robot 100 may also comprise a movement controller 1116 forcontrolling the movement of the mobile robot 100. It receivespositioning information from the positioning unit 1110 on the currentposition and receives from the processing unit 1100 information on atarget position. The movement controller 1116 then steers the motors1118 of the mobile robot 100 such that a targeted position is reached.The movement controller 1116 may also control the balance and directionof the mobile robot 100 as such and by that ensure a stable radiocoverage sub-area 130 on the ground.

The mobile robot 100 may also comprise motors 1118 for movement andbalance of the mobile robot 100 and/or to maintain a given geographicalposition 200.

The mobile robot 100 may also comprise an energy supply module 1120 usedto produce electrical energy needed for the operation of the mobilerobot 100 and of the radio base station 150. This energy supply module1120 may further comprise batteries, a generator, and spare fuel.

Referring to FIG. 12, this figure shows a block diagram illustrating amaintenance base, according to the invention. The illustrated entity maycorrespond to the maintenance base 110. The maintenance base 110 may beadapted to perform one or more steps of the above described method shownin FIG. 9 or FIG. 10.

The maintenance base 110 may comprise a number of functional units,which are described in further detail below and which are adapted toperform respective method steps.

A processing unit 1200 of the maintenance base 110 may be adapted toprocess status reports received from mobile robots 100, to determine acritical operational status of a mobile robots 100, to trigger acircular shift operation within a daisy chain loop 300, to determinegeographical positions 200 for mobile robots 100, to instruct mobilerobots 100 to take up a geographical positions 200, to instruct a mobilerobot 100 to return to the maintenance base 110, to deploy a furthermobile robot 100 to a vacant geographical position, to re-arrange thedeployment of mobile robots 100 to geographical positions 200, or todetermine a daisy chain loop 300 of deployed mobile robots 100 and themaintenance base 110. In a practical implementation the processing unit1200 may be one processor taking care of all the above functions, or mayalso be distributed over more than one processor, wherein the functionsare distributed over the available processors.

The maintenance base 110 may further comprise a sending unit 1202 and areceiving unit 1204 via which the maintenance base 110 can communicatewith the mobile robots 100. The sending unit 1202 may send out signalingmessages composed by the processing unit 1200. The receiving unit 1204may receive signaling messages from other mobile robots 100, and forwardthe received signaling messages to the processing unit 1200 forprocessing. The maintenance base 110 may comprise more than one sendingunit and receiving unit for signaling capacity and redundancy reasons.

The maintenance base 110 may further comprise a wireless communicationnetwork interface 1206 for connecting the radio base stations 150mounted on mobile robots 100 to the access network of the wirelesscommunication network. This interface is used for calls and sessionsongoing in the mounted radio base stations 150 and for performing userequipment 120 handover between mounted radio base stations 150 andbetween land-based radio base stations and mounted radio base stations150. The maintenance base 110 may comprise more than one wirelesscommunication network interface 1206 for signaling capacity andredundancy reasons.

The maintenance base 110 may also comprise a storing unit 1208 relatedto operations for providing coverage of a wireless communicationnetwork. The storing unit 1208 may comprise various types of memory suchas volatile memory, non-volatile memory, hard disk drives, solid statedrives, a network interface to a database or a data center, securedigital cards, or hardware such as smart cards, non-reversible chips,security chips, security modules, or trusted platform module devices.The storing unit 1208 may be used by the processing unit 1200 forstoring information, for example program code.

The maintenance base 110 may further comprise an operational statusdetermination unit 1210 for determination of the status of the mobilerobots 100. The operational status determination unit 1210 may receive astatus report from the mobile robots 100. The operational statusdetermination unit 1210 may also query a status from a mobile robot 100.Received status information may be stored/logged for statistical oroptimization purposes. The processing unit 1200 may determine a criticaloperational status of a mobile robot 100 with the help of theoperational status determination unit 1210.

The maintenance base 110 may further comprise a daisy chain loopdetermination unit 1212 for determination of one or several daisy chainloops 300. The daisy chain loop determination unit 1212 allocatesdeployed mobile robots 100 to daisy chain loops 300. The number ofmobile robots 100 determines the time until a mobile robot 100 canreturn to the maintenance base 110 for maintenance, considering forexample movability of the mobile robots 100. Movability may be relatedto a moving speed, a reaching range, a regular maintenance interval, anda recharging/refueling interval of the mobile robots 100. Furtherconsidered may be a size of the radio coverage area 140 generated by theradio base stations 150 mounted on mobile robots 100, a shape of thecoverage area of the wireless communication network, a capacity of thecoverage area of the wireless communication network, or a maximumpayload of the mobile robots 100.

The maintenance base 110 may further comprise a geographical positiondetermination unit 1214 for determination of the geographical positions200 for deployed mobile robots 100 to generate the targeted radiocoverage area 140. The geographical position determination unit 1214determines the geographical positions 200 suited to provide the targetedradio coverage area 140.

The maintenance base 110 may further comprise a circular shift operationtrigger interval determination unit 1216, for determination of theperiodic circular shift operation trigger interval. Circular shiftoperations within a daisy chain loop 300 are triggered at periodicintervals, and the interval is determined in such a way that mobilerobots 100 return to the maintenance base 110 by circular shiftoperations within the daisy chain loop 300, before the mobile robots 100reach a critical operational status.

The maintenance base 110 may further comprise spare mobile robots 1218for replacement of failing mobile robot 600 or for filling vacantgeographical position 200 in daisy chain loops 300. This unit 1218 mayalso comprise spare parts for mobile robots 100 needed repairing mobilerobots 100 and/or for periodic maintenance work.

The maintenance base 110 may further comprise energy/fuel storage 1220for recharging/refueling of mobile robots 100 returning to themaintenance base 110 for periodic maintenance purposes. This module maycomprise a fuel tank, batteries, power generator, and/or a connection tothe public electricity grid.

According to another embodiment, a computer program is provided. Thecomputer program may be executed by the processing units 1100 and/or1200 of the above mentioned entities 100 and/or 110 respectively suchthat a method for providing coverage of a wireless communication networkas described above with reference to FIGS. 7 to 10 may be carried out orbe controlled. In particular, the entities 100 and/or 110 may be causedto operate in accordance with the above described method by executingthe computer program.

The computer program may be embodied as computer code, for example of acomputer program product. The computer program product may be stored ona computer readable medium, for example a disk or the storing unit 1108and/or 1208 of the entities 100 and/or 110, or may be configured asdownloadable information.

One or more embodiments as described above may enable at least one ofthe following technical effects:

-   -   Provide coverage of a mobile communication network with base        stations mounted on mobile robots    -   Cheap deployment of the mobile robots    -   Expand the network coverage quickly where needed and/or when        needed    -   Expand the network capacity quickly where needed and/or when        needed    -   Cheap coverage of remote or distant places    -   Quick removal of the coverage/capacity expansion    -   Fast replacement in case of unexpected mobile robot failure    -   Perform regular maintenance of deployed mobile robots without        any degradation of the radio coverage range and/or capacity    -   Adjusted measurement reports of user equipment for handover        secure successful handover between two radio coverage sub-areas

Modifications and other embodiments of the disclosed invention will cometo mind to one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is to be understood that the embodiments are not to belimited to the specific embodiments disclosed and that modifications andother embodiments are intended to be included within the scope of thisdisclosure. Although specific terms may be employed herein, they areused in a generic and descriptive sense only and not for purposes oflimitation.

The invention claimed is:
 1. A method for providing coverage of awireless communication network, the wireless communication networkcomprising radio base stations mounted on mobile robots, the mobilerobots being capable of communicating with a maintenance base, themethod comprising: determining a radio coverage area to be provided bythe radio base stations mounted on the mobile robots; deploying themobile robots at geographical positions suitable to provide the radiocoverage area; in order to maintain the radio coverage area, themaintenance base replacing a deployed mobile robot by: instructing thedeployed mobile robot to be replaced to return to the maintenance base;deploying a further mobile robot to a vacant geographical position; andrearranging the deployment of the mobile robots to geographicalpositions, the rearranging comprising determining a daisy chain loop ofdeployed mobile robots and the maintenance base; wherein the maintenancebase is allocated to the daisy chain loop as an entry/exit elementsupporting a circular shift operation performed by the mobile robots ofthe daisy chain loop in which a last mobile robot of the daisy chainloop returns to the maintenance base and a further mobile robot deploysto a vacant first position of the daisy chain loop.
 2. The method ofclaim 1, wherein the mobile robots are instructed by the maintenancebase to take up their geographical positions by moving along a path ofthe daisy chain loop starting from the maintenance base.
 3. The methodof claim 1, wherein the mobile robots are instructed by the maintenancebase to take up their determined geographical positions by movingstraight from the maintenance base to their determined geographicalpositions.
 4. The method of claim 1, wherein the circular shiftoperation within the daisy chain loop is triggered at periodic intervalsby the maintenance base.
 5. The method of claim 4, wherein the periodicinterval is determined such that mobile robots of the daisy chain loopare shifted to the maintenance base by circular shift operations beforereaching a critical operational status.
 6. The method of claim 1,wherein the circular shift operation within the daisy chain loop istriggered by one of the mobile robots of the daisy chain loop.
 7. Amethod of operating a maintenance base for providing coverage of awireless communication network, the wireless communication networkcomprising radio base stations mounted on mobile robots, the mobilerobots being capable of communicating with the maintenance base, themethod comprising: deploying the mobile robots at geographicalpositions, determined to be suitable to provide a radio coverage area,by instructing them to take up their determined geographical positions;in order to maintain the radio coverage area, the maintenance basereplacing a deployed mobile robot by: instructing the deployed mobilerobot to be replaced to return to the maintenance base; deploying afurther mobile robot to a vacant geographical position; and rearrangingthe deployment of the mobile robots to geographical positions; whereinthe rearranging the deployment of the mobile robots to geographicalpositions comprises: determining a daisy chain loop of deployed mobilerobots and the maintenance base, wherein the maintenance base isallocated to the daisy chain loop as an entry/exit element; andinstructing the mobile robots of the daisy chain loop to perform acircular shift operation within the daisy chain loop in which the lastmobile robot of the daisy chain loop returns to the maintenance base,and a further mobile robot is deployed to a vacant first position of thedaisy chain loop.
 8. The method of claim 7, further comprisingdetermining the geographical positions for the mobile robots suitable toprovide a radio coverage area.
 9. The method of claim 7, wherein themaintenance base determines a radio coverage area to be provided by theradio base stations mounted on the mobile robots.
 10. The method ofclaim 7, wherein the mobile robots are instructed to take up theirgeographical positions by moving along a path of the daisy chain loopstarting from the maintenance base.
 11. The method of claim 7, whereinthe mobile robots are instructed to take up their determinedgeographical positions by moving straight from the maintenance base totheir determined geographical positions.
 12. The method of claim 7,wherein the circular shift operation within the daisy chain loop istriggered at periodic intervals by the maintenance base.
 13. The methodof claim 12, wherein the periodic interval is determined such thatmobile robots of the daisy chain loop are shifted to the maintenancebase by circular shift operations before reaching a critical operationalstatus.
 14. The method of claim 7, wherein a trigger is received fromone of the mobile robots of the daisy chain loop to instruct thecircular shift operation of the mobile robots of the daisy chain loop.15. The method of claim 7, wherein the mobile robots are instructed toperform the circular shift operation by permanently moving from theircurrent geographical position to a further geographical position of thedaisy chain loop.
 16. The method of claim 7, further comprising:receiving a status report from a deployed mobile robot comprising anoperational status of the deployed mobile robot; determining theoperational status to be critical; and sending an instruction to themobile robot associated with the status report to return to themaintenance base.
 17. The method of claim 7, further comprising sendingan instruction to a mobile robot for handing over a handling of ongoingcalls and/or packet sessions from the mobile robot to a further mobilerobot.
 18. A maintenance base for providing coverage of a wirelesscommunication network, the wireless communication network comprisingradio base stations mounted on mobile robots, the mobile robots beingcapable of communicating with the maintenance base, the maintenance basecomprising: one or more processors; memory containing instructionsexecutable by the one or more processors whereby the maintenance base isoperative to: deploy the mobile robots at geographical positions,determined to be suitable to provide a radio coverage area, byinstructing them to take up their determined geographical positions; inorder to maintain the radio coverage area, replace a deployed mobilerobot by: instructing the deployed mobile robot to be replaced to returnto the maintenance base; deploying a further mobile robot to a vacantgeographical position; and rearranging the deployment of the mobilerobots to geographical positions; wherein to rearrange the deployment ofthe mobile robots to geographical positions the maintenance base isoperative to: determine a daisy chain loop of deployed mobile robots andthe maintenance base, wherein the maintenance base is allocated to thedaisy chain loop as an entry/exit element; and instruct the mobilerobots of the daisy chain loop to perform a circular shift operationwithin the daisy chain loop, wherein the last mobile robot of the daisychain loop is returning to the maintenance base, and a further mobilerobot is deployed to a vacant first position of the daisy chain loop.19. The maintenance base of claim 18, wherein the instructions are suchthat the maintenance base is operative to determine the geographicalpositions for the mobile robots suitable to provide a radio coveragearea.
 20. The maintenance base of claim 19, wherein the instructions aresuch that the maintenance base is operative to determine the radiocoverage area to be provided by the radio base stations mounted on themobile robots.
 21. A system for providing coverage of a wirelesscommunication network, the wireless communication network comprisingradio base stations mounted on mobile robots, the mobile robots beingcapable of communicating with a maintenance base, the system comprising:a plurality of the mobile robots; at least one user equipment; themaintenance base, the maintenance base comprising: one or moreprocessors; memory containing instructions executable by the one or moreprocessors whereby the maintenance base is operative to: deploy themobile robots at geographical positions, determined to be suitable toprovide a radio coverage area, by instructing them to take up theirdetermined geographical positions; in order to maintain the radiocoverage area, replace a deployed mobile robot by: instructing thedeployed mobile robot to be replaced to return to the maintenance base;deploying a further mobile robot to a vacant geographical position; andrearranging the deployment of the mobile robots to geographicalpositions; wherein to rearrange the deployment of the mobile robots togeographical positions the maintenance base is operative to: determine adaisy chain loop of deployed mobile robots and the maintenance base,wherein the maintenance base is allocated to the daisy chain loop as anentry/exit element; and instruct the mobile robots of the daisy chainloop to perform a circular shift operation within the daisy chain loop,wherein the last mobile robot of the daisy chain loop is returning tothe maintenance base, and a further mobile robot is deployed to a vacantfirst position of the daisy chain loop.
 22. The system of claim 21,wherein the instructions are such that the maintenance base is operativeto determine the geographical positions for the mobile robots suitableto provide a radio coverage area.
 23. A computer program product storedin a non-transitory computer readable medium for controlling operationof a maintenance base for providing coverage of a wireless communicationnetwork, the wireless communication network comprising radio basestations mounted on mobile robots, the mobile robots being capable ofcommunicating with the maintenance base, the computer program productcomprising software instructions which, when run on one or moreprocessors of the maintenance base, causes the maintenance base to:deploy the mobile robots at geographical positions, suitable to providea radio coverage area, by instructing them to take up their determinedgeographical positions; in order to maintain the radio coverage area,replace a deployed mobile robot by: instructing the deployed mobilerobot to be replaced to return to the maintenance base; deploying afurther mobile robot to a vacant geographical position; and rearrangingthe deployment of the mobile robots to geographical positions; whereinto rearrange the deployment of the mobile robots to geographicalpositions the software instructions cause the maintenance base to:determine a daisy chain loop of deployed mobile robots and themaintenance base, wherein the maintenance base is allocated to the daisychain loop as an entry/exit element; and instruct the mobile robots ofthe daisy chain loop to perform a circular shift operation within thedaisy chain loop, wherein the last mobile robot of the daisy chain loopis returning to the maintenance base, and a further mobile robot isdeployed to a vacant first position of the daisy chain loop.
 24. Thecomputer program product of claim 23, wherein the instructions are suchthat the maintenance base is operative to determine the geographicalpositions for the mobile robots suitable to provide a radio coveragearea.